Call dumber indicator



April 14, 1931.

E. ZOLLER ET AL (24am. NUMBER INDICATOR Filed June 4. 1929 4 Sheets-Sheet 1 //7 ventons:

6-3 f-v w" A ril 14, 1931. ZOI-LER ET AL CALL iwMBER INDICATOR Filed June 4, 1929 4 Sheets-Sheet 2 /n ventorg; we?

April 14, 1931. E. ZOLLER ET AL 1,800,240

CALL NUMBER INDI CATOR Filed June 4, 1929 4 Sheets-Sheet 5 lnventons:

April 14, 1931. E ZOLLER ET AL 1,800,240

0511, NUMBER INDICATOR Filed June 4, 1929 4 Sheets-Sheet 4 IIIIIIIIIA Illlllllllllll a QR 4 Patented A pr.14,' 19 31 PATENT OFFICE EGON ZOLLEB AND JOSE]? VILLIGER, OF MAILAND, ITALY cur-NUMBER mmca'ron Application filed June 4, 1929, Serial No. 868,314, and in Germany August 4, 1928.

It is desirable that in telephone installations with selector system the number of the caller is registered at the called subscriber, even without the intention of the caller, so

' B that the called subscriber can ascertain every time from which number he has been called, als0, when the caller does not; give himself this number, this problem having up to now not been solved.

1 It is further desirable that in telephone installations with selector systemthe caller must be in osition to transmit agreed signs by means oi this number disc in the absence of the called subscriber. This problem has also not been solved up to the present.

These problems can be solved according to the invention, by adding to the calling apparatus a device, comprising a contact system formed of the number of the calling apparatus and which, after selecting and connection with the called telephone, functions automatically and at the same time connects the resistance parallel to the subscribers line which remains connected and makes it possible to transmit other signs with the aid of the usual number disc. Thisresistance is I dimensioned so that during the interruptions of the impulse contact the feeding current in the subscribers loop is not interrupted but reduced to a minimum, so that the corresponding li'ne relays in the central station remain attracted, whereby the connection be tween the calling apparatus and the receiving apparatus remains preserved- The current impulses act then no longer in the central station but merely inductively in the subscribers loop of. the called apparatus, where the receiving apparatus transmits the current impulses upon an auxiliary circuit in which they are recorded by a recording device.

An embodiment of the invention is illustrated by way of example in the accompanying drawings in which:

Fig. 1 shows diagrammatically an ordinary subscribers apparatus however with the arrangement by which, also without the intention of the caller, his number is recorded at the called subscriber. Fig. 2 shows diagrammatically the apparatus of the called subscriber and the connection necessary for operating the recording device.

Fig. 3 shows the connection of the calling apparatus through an automatic selector cen- 65 tral station to the called apparatus during the impulse transmission.

Fig. 4 shows in part elevation the arrangement of the commonly used number disc and of the improved disc, releasing automatically and indicating the call number.

Fig. 5 is a side elevation of Fig. 4, the number disc being omitted.

Fig. 6 is a section through Fig. 5.

Fig. 7 is a rear elevation of the Figs. 4, 5 and 6.

Fig. 8 shows a portion of the top plan View of the Figs. 4, 5 and 6.

Figure 9 is a side View showing the driving mechanism of Figure 2; F Figure 10 is a part view on line CD of igure 11 is a view on line AB of Fig. 9;

Figure 12 is a section of part of mechanism shown in Fig. '9;

Continuous current flows from the central station C, after the telephone receiver has been removed, through the wires 1 and 2 into the calling station A. Through the wires 3 and 4 alternating current is sent after the selection from the central station C to the called station E. 5 is the alarm, 6 the condenser, 7 the receiver contact lever which, after removing of the telephonereceiver, closes the talking circuit at the contact point 8-, 9 is a microphone, 10 a transmitter coil, 11 the telephone receiver, 12 the impulse contact actuated by the number disc and 13 the short circuit contact. By removing of the telephone receiver continuous current flows in a well known manner from the central station through'the wire 1 to the contact point 7, 8', transmitter coil 10, microphone 9, impulse contact 12, wire 2 back to the central station C. This current excites in a known manner in the central station C the relays 14 of the electric arrangements. ccording to the number selected alternating current flows now from the central station C through the wires 3 and 4 to the called station E, i. e. from the wire '5 is operated, whereby the alternating current is replaced by the feed current (talking current).

The invention consists of an arrangement on the call station A and in special connection arrangements in the called station B. A form of construction of the apparatus to be mounted in the call station A will be first described.

The usual number disc 15 (Figs. 4 and 8) is rigid with a coaxial spur wheel 16, which meshes with a spur wheel 17 keyed on a shaft 18 journaled in the wall 51 of the casing. On the rear side of the spur wheel 17 a pawl 19 is loosely mountedwhich, when the spur wheel 7 rotates in the one direction, pushes forward a ratchet wheel 20. When the spur wheel 17 rotates in the other direction, the ratchet wheel 20 is locked by a lockingpawl 21, loosely mounted on wall 51 of the casing (Fig. 5), so that this ratchet wheel cannot rotate. The ratchet wheel 20 is keyed on a sleeve 22, rotatably mounted on shaft 18. On this sleeve 22 two discs 25 and 26 are further loosely mounted forming together a spring barrel and containing two pre-tensioned springs 23 and;24 the inner ends of which are fixed to the hooks 88 of sleeve 22, the outer ends of the springs being attached to friction rings 27. The disc 25 rves as moving ahead disc. The disc, 26, on which for instance a contact system 62 is arranged corresponding to the connection number of the caller. Will be hereinafter called type disc. The spur wheel'li has on the front side a cam disc 28 with cam 29. Against the rim of the cam disc bears the free end of a lever 30 keyed on a shaft 32. On the moving ahead disc 25 a stop 33 is arranged,

against which bears the free end of a lever 31 keyed .on shaft 32. The moving ahead disc ,25 has further a cam 54 (Fig. 1).

On the shaft 18 a spur wheel '35 and a spur wheel. 37 are loosely mounted, the latter being rigidlyconnected to a ratchet wheel 38 by means of a bush 89. On this bush 89 a catch disk having an abutme'nt46 is loosely. mounted between the spur wheel 37 and the ratchet wheel 38. The catch disc 40 carries further a pin 90 onwhich a lever 41 and a catch pawl'43 rigidly connected with 4 each other are loosely mounted. On shaft 18 a curve disc 39 is further keyed on which two catch pins 45 and .47 are fixed. The

' lever 41 is pressed, by the action of a pressure spring 44:, against the rim of the curve end of said spring bearing against by the winding aecaaae 'a bridge 34 is fixed in which two axles 91 and 92are mounted on which two spur wheels 93, 94. are loosely mounted and mesh with each other. The spur wheel 93 meshes further with the spur wheel 35, the spur wheel 94 meshing with the spurwheel 37 acting thus as reversing gear. The spur wheel 35 has on the inner surface a ringshaped projection 52 on which one end of the friction spring 36 is fixed, the other free a ringshaped projection 53 on the outer surface of the moving ahead disc 25. On shaft 32 a lever 18 is loosely mounted which has an abutment 97 and is connected to the hook 7 of the telephone receiver. On this shaft 32 a lever 49 havin a nose 98 and an end face 106 (Figs. fl an 1). The discs 25 and 26-have teeth 95, 96 respectively in their circumference meshing with spur wheels 99 and 100 respectivel loosely mounted on a shaft 101. The sha t 101 is. journaled in the casing wall 51and 8) is further loosely ar ranged. On the type disc 26 a pin is provided and further an indentation (Fig.

connected to a regulating brake 102. On

the shaft 101 a ratchet wheel 103 is keyed which is rotated by ratchet cones 104 andl05 mounted on the spur wheels 99 and 100.respectively.

The mechanical operation is as follows:

' In the call station A two different efiects take place during the number selection i. e. and by the releasing of the number disc 15. The one effect serves to accumulate the spring power, the other efiect consisting in controlling the type disc.

By the rotation of the number disc 15 the sha t 18 is rotated forward and backward according to the direction of rotation of the number disc, through the intermediary of the spur wheels 16 and 17 (Fig. 4). During the forward rotation of the number disc 15 the ratchet wheel 20 and through the same the sleeve 22, is rotated by the pawl 19 in the direction of the arrow line I) (Fig. 4:). At

the backward rotation of the number disc 15 or of the spur wheels 16 and 17 the ratchet .wheel 20 is locked by the ratchet pawl 21 so that the springs 23 and 24 are put under tension. When these springs have been completely put under tension, the friction rings "27 enter into function so that further lifted a moment releasing the abutment 33 of the moving ahead disc 25.

' The curve disc 39 has also been rotated by the shaft 18 during the forward rotation of the number disc 15 (Figs. 5, 6 and 7) so that the curve 42 of this curve disc 39 has rotated in the direction of the arrow line a under the lever 41 and the catch pawl 43 has been brought into engagement with the ratchet wheel 38 by the pressure of spring 44. The catch pin 45 of the curve disc 39 has come to bear against the abutment 46 of the catch disc 40, whereby this catch disc with the ratchet wheel 38 have been rotated also in the direction of the arrow line 0.. By this rotation of the ratchet wheel 38 the moving ahead disc 25 is retained in its initial position through the intermediary of spur wheel 37, reversing gear 92,93, spur wheel 35 and friction 52, 53. At the backward rotation of the number disc 15 or of shaft 18 and consequentlyalso of the curve disc 39 the catch pin 47 comes to bear against the abutment 46 and turns the catch disc 40 back into its initial position; The curve 42 has thus been dis-.

placed into the position indicated in Fig. 7. The lever 41 is lifted so that the catch pawl 43 disengages from the ratchet wheel 38. At the same time the cam 29 of the cam disc 28 has again moved under the lever 30 and lifted again the lever 31 so that the moving ahead disc 25 is released. If in this position no further selecting takes place and consequently no backward rotation of the moving ahead disc 25 by the reversing gear 92, 93, the disc 25 begins to run down in the direction of the arrow line b by the action of its tensioned spring 23 (Fig. 4). a The type disc 26 remains still locked by the pin 50 on the nose 98 of the lever 49. If the moving ahead disc 25 has carried out its rotation in the direction of the arrow line b (Fig. 4) so far, that the abutment 33 strikes against the face 106 of the lever 49, this lever is lifted and releases the type disc 26. 7

The type disc 26 runs then down under the action of its tensioned spring 24 in the same direction (arrow line b Fig. 4) until thepin 50 strikes against the pin 33 which has moved ahead and been stopped by the abutment 97 of the lever 48. The releasing lever 48 is connected with hook 7 of the telephone receiver and has been lowered into this position owing to the receiver having been hung on. The object is to prevent the moving ahead disc 25 to further rotate up to its ini-v tial position.

The type disc 26 is also stopped after one rotation. The stopping of the moving ahead disc 25 in this position serves further to stop the cam 54 (Fig. 1) under the contact 55 so that the resistance 56 remains switched in in the line 12. The type disc 26 operates, during its running down movement, the im ulse contact 61 by its contact system 62. T e running down of the two-discs 25 and 26is singly regulated to form a temporary running down by the common regulating brake- 102 through the intermediary of the spur wheels 99 and 100 and ratchet wheel 103.

When the receiver is hung on hook 7, the abutment 97 of the lever 48 is lifted to in front of the pin 33. The two discs 25 and 26 complete thereby their rotation and the resistance 56 is consequently cut out by opening of the contact 55.

The electrical operation of this arrangement is as follows: 7

After turning down of the moving ahead disc 25 the cam 54 (Fig. 1) has been shifted under the contact 55 and closed this contact whereby the resistance 56 is parallel connected to the line 12. As soon as the type disc 26 rotates, the contact 57 is closed, and

then the contact 58 opened, as the cam 59 i has been lifted out of the indentation 60. The feed current flows then through wire 1, impulse contact 61 and contact 57 to the wire 2, so that this wire is short circuited. The impulse pins 62, arranged on the type disc 26 according to the 'subscribers own number, operate during the running'down of disc 26 the'feeler 63 and thereby the impulse contact 61. When the impulse contact 61 is being opened, the feed circuit is not interrupted as there does still flow a holding current from wire 1 through contact 55 and resistance 56 to the wire 2, whereby the relays 14 in the central station C remain attracted-and consequently the impulses do no longer act in the central station but directly in the wires'3 and- .59 has dropped into the indentation -of disc 26.v The resistance 56 remains however switched in until the telephone receiver is In order to positively intersect and record these impulses in the apparatus of the station A with regard to the running down of the type disc and consequently to the indications of its own subscribers number and then also current impulses adapted to be arbitrarily produced, the following arrangement has been made in the apparatus B.

An electromagnetic driving device (Fig. 9) is provided consisting of a permanent magnet 107, the pole pieces 108 of which directed a constant magnetic field on-the armature 64. Y The armature 64 is alternately polarized by the coil 65 through the call current. The armature 64 is mounted on the shaft 109 which is rotatably journalled in the wall 110 of thecasing. On the shaft 109 the lever 111 and one end of spring 112 is rigidly mounted. The other end of the spring 112 is fastened in the casing wall 110. The

wheel 113 connected with toothed wheel 114 and sleeve 115 are rotatably mounted on the shaft 109. A loose spring 116 lies on the sleeve 115 and on the sleeve of the casing wall 110 and acts as lock for the wheels 113 and 114. Thecontact actuating arm 66 with the stop 117 is also rotatable on the shaft-109.

The toothed wheel 119, ratchet wheel 120 and catch 79 are keyed on the shaft 118,

which is rotatably journaled in the. casing wall 110. The toothed wheel 121 and the.

spring casing 122 are rotatably mounted on the shaft 118. The outer end of the spring 123 is rigidly connected with the spring casing 122, whereas the inner end of the spring 123 is fastened on the shaft 118. On .the spring casing 122 the pawl 124 is oscillatably mounted and is pressed against the ratchet 120 by the spring 125. On the casing wall 110 a pawl 139 is also arranged, which is pressed by the spring 140 onto the locking toothed wheel 141 of the spring casing 122.

The toothed rim 126 of the spring casing 122 meshes with a pinion 127 keyed on a shaft 128, which is rotatably mounted in the casing wall 110. The air brake 129 is also rigidly mounted on the shaft 128.

The toothed wheel 130 is rotatably mounted in the lever 131, the pivot 132 of which is also rotatably mounted in the casing wall 110. The surface 133 of the lever 131 acts as armature and is operated by the core'134l, on which the coil 135 is mounted.

On the lever 111. two screws 136 are fastened, on which the feed wheels 137 are eccentrically' and rotatably mounted, which wheels arep'ressed against the wheel 113 by the sprihg 138. The contacts 67, 68, 69 and are fastened on the casing wall 110 (Fig. 11). When alternating current (calling current) is supplied to the driving device 78 (Figs.

2, 9 to 12) the current flows through the windings 135 and 65. armature 133 attracts the clutch 81 and causes through the lever 131 the engagement of the toothed wheel 130 in the two toothed wheels 119 and 121, which are thereby coupled. At the same time the armature 64 oscillates' through the adjusted spring 112 synchronously to the number of periods of the. alternating current and shifts the wheel 113 in the direction of the arrow through the lever 111 and the wheels 137. Consequently, the catch 79 also moves forward in the direction of the arrow'through the-toothed wheels 114, 121, 130, 119 and the shaft 118. At the same time the spring 123 is tensioned and the spring casing 122 locked bv-the pawl 139.

,During the pauses of the calling current impulses, which eflects the disengagement of the wheels 119 and 121; the catch 79 is turned back by the tensioned spring 123.

Consequently the wheel 120' pinion 127 and shaft 128 so that the return move'mentis smaller than the feed and conse uently after repeated calling current imp s the catch 79 reaches its extreme position and consequently the stop 117 actuates the contact actuating arm 66 and closes the contact 70.

The contacts 68 and 169 are auxiliary contacts which during the corresponding switching proceedin bridge the relay 73, in order that the impu ses thereby produced are not recorded.

There is further rovided a control relay 71, a throttling coil 72, a highlysensitive polarizer relay 73 (for induction currents) and a condenser 7t.

In a separate auxiliary circuit (for instance light current) a writing magnet 76 and for instance a magnet 77 for conveying the ribbon are inserted.

pawl 124, toothed 126,

If any subscriber A calls the station B oscillate and shifts stepwise the catch 79 which in its; initial position liberates the contact actuatlng arm 66 from the position v. shown into the medium position. The releasing contact 67 is thereby closed and the auxiliary contact 68 opened.

After repeated calling current impulses the catch 79 has arrived in its extreme position and shifted the arm 66 from its medium position towards the auxiliary contact 69 and the control contact 70, whereby the feeding circuit is closed, the alternating current suppressed and consequently the connection between station A and station B established through the selecting central station 6. The continuous current flows then through wire 3, control contact 70, releasing contact 67 relay 71, impulse contact 12 to wire 4.

The relay 71 oscillates the contacts 80.and

81- into the position 11 and closes the contacts 82 and 83 of the auxiliary circuit 75, which excites the conveying magnet 77 for the typing ribbon. The contact 86 of the relay 73 closes and opens during the impulse transmission the circuit of the writing magnet in accordance with the-current impulses.

At this suppressing of the alternating current the catch 79 is slowly turned back into its initial position by the coupling 84 and by a spring which has been put under tension during the forward feeding.

At the beginning of the retrograde move-.

ment of the catch 79 the contact arm 66 is released again to assume the medium position, whereby the contacts 69 and 70 are opened. By opening the contact point 70 the current flows through line 3, 80 position II- 72 67, 71, 12, wire 4. 4

By switching the throttlingv coil 72 in the circuit the current intensity in the same is reduced so that in the subscribers loop B only a holding current flows also, whereby the voltage in the station B is increased and the line rela s 85 in the central station are held so that t e connection remains.

These switching proceedings in the apparatus' A and B are in relation in the following manner:

Before the called subscribed removes the telephone receiver of his apparatus the type disc 26 in the caller station A has already been released and transmits the subscriber number of the caller to the station B of the called subscriber so that the latter can controlthe number of the caller before he receives the communication. If the called subscriber is absent, the caller can transmit communications by his'number disc 15, his call number having been recorded in the called apparatus by the running down of the type disc even without intention of the caller as the receiving device in the apparatus B is ready for reception also after the receiving of the number positively transmitted from station A by the running down of the type disc 26 and owing to the retarded moving backward of the device 66 to 79 in 78.

These last mentioned proceedings, i. e. when the caller by means of its number disc transmits to the called further communica tions, do not prevent that the called subscriber receives the communication. When the called subscriber removes the telephone receiver, the recording apparatus in B is stopped. p v

The releasingof thedevice in B operates in the following manner:

When the catch-79 has again assumedits initial position and the contact arm 6 has been shifted from its medium position into the releasing position, it interru ts the releasing contact 67 after closing 0 the auxiliary contact 68. The relay 71 of'the station B and the relays 85 in the central station C drop off, and the telephone and the arrangement in B described are free again;

We claim:

1. An arrangement for positively indicating the call number or other-signs of a calling. subscriber in the called subscribers station by the number disc in automatic connectin telephone installations, comprising in the ca led station a resistance adapted to be connected in parallel to the feed wires of this station sothat the inductive current impulses produced after the selecting by the caller remain inefi'ective on the line relay of the central station acting merely in the loop of the called subscribers station; an auxiliary circuit in the called subscribers station to which said current impulses are transmitted, and

an indicating device inserted in said auxilia circuit and operated by said current imp ses.

2. An arrangement as specified in claim 1, comprising in combination with the resistance in a callers station and with the number disc in this station, a type disc coupled with said number disc comprising a si contact s stem; adapted to be automatica y connecte in parallel after the selecting of the number to be called said resistance to the feed line and to transmit corresponding signs into the loop of the receiving station.

3. An arrangement for positively indicatng the call number or other signs of a calling subscriber in the called subscribers station by the number disc in automatic connecting telephone installations, comprising in the caller station a resistance adapted to be connected in parallel to the feed wires of this station atthe number selecting and to remain switched in until it is cut out by the telephone receiver being hung on and dimensioned so that the inductive current impulses produced after the selecting by the caller remain ineflective on the line relay of the central station acting merely in the loop of the called subscribers station, an auxiliary circuit in the called subscribers station to which said current impulses are transmitted, and an indicating device inserted in said auxiliary circuit and operated by said current impulses.

i. An arrangement as specified in claim 1, compr sing in combination with the resistance and with the number disk in the callers station, a type disc coupled with said number disc, a sign contact system fixed on said type disc adapted to automatically connect in parallel said resistance to the feed line after the selection of the called number and transmit correspondingsigns into the loop of the called station, aratchet wheel rotated from said number disc at the'number selected, a rotatable sleeve on which said ratchet wheel is keyed and said ty e disc is loosely mounted, a moving ahea disc loosely mounted on said sleeve, said type disc and said moving ahead disc forming together a spring barrel, two springs in said spring barrel hooked each with one end to said sleeve the other free ends actin respectively on said type disc and on said moving ahead disc, a cam disc rotated from said number disc, levers, abutments, and pawls between said cam disc and said type disc for liberating said type disc at the termination of the rotation of sald number disc at number selecting.

5. An arrangement as'specified in claim 1, comprising in combination with the resistance and with the number disc in the callers station, a type disc coupled with said number disc, signs fixed on said type disc adapted to automatically connect said resistance in parallel to the feed line after the selection of the'called number and to transmit correspondaratchet wheelrotat'e from said number disc at the number selecting, a rotatable sleeve on which said ratchet wheel is' keyed and said a disc is loosely mounted, a moving ahead sc loosely mounted on said sleeve said type -cu1t 1n the called station a throttlm cell, a

disc and said moving, ahead disc iormin together a spring barrel, two springs in em spring barrel hooked each with one end to said sleeve the other free ends actin respectively on said type disc and on sai moving.

ahead disc, a cam disc rotated from said numr disc, levers, abutments, and parts between said cam disc and said type disc for liberating said type disc at the termination of the rotation of said number disc at number selecting, and two pins for locking said moving ahead disc and said type disc prior to and during the number selecting. 6.4 An arrangement as specified in claim 1, comprising in combination with the resistance and with the number disc in the caller s station, a type disc coupled withsaid number disc, signs of a contact system fixed on said t e disc adapted to automatically connect sa1d resistance to the feed line after the selection of the called number and tdtransmit corresponding signs into the loop of the called station, a ratchet wheel rotated from to said number disc at the number selecting, a

rotatable sleeve on which'said ratchet wheel is keyed and said type disc is loosely mounted, a moving ahead disc loosely mounted on said sleeve said type disc and said moving ahead disc forming together-a spring barrel, two springs in said spring barrel hooked each with one end to said sleeve the other free ends acting res ectively on said type disc and on said moving ahead disc, a cam disc rotated from a number disc, levers, abutments, and parts between said cam disc and said type disc for liberating said type disc at the termi-- nation of the rotation of said number disc at number selecting, two pins for locking said moving ahead disc and said type disc prior to and during the number selecting, a cam on said moving ahead disc, a contact adapted to be closed by said cam after the liberating of said moving ahead disc to switch into circuit said resistance until at the hangin u of the telephone receiver said moving ahead disc is rotated again.

7. An arrangement as specified in claim 1, comprising in the called station a switch device consisting of an oscillatable contact arm, a releasing contact closed by said arm at the beginning of its operative oscillation, an auxiliary contact opened at the beginning of the operative oscillation, of said arm, a sec ond auxiliary contact, and a control contact both adapted to be closed at the end of the ophea set the beginning of the retrograde oscillation at said contact arm said rel r H contact I" v tainingsaid feed circuit until e trtter signs have been recorded.

8. An arrangement as specified inclaim 1", comprising in combination with the feed circontrol relay series-connected to sai ttling coil adapted to close said circuit, a condenser, a high sensitive larized relay series connected to said con enser said condenserand said polarized relay be in par'el connection with to said series-connected throttling coil and control relay,

"9. An arrangement as specified in cla 1, comprising in combination with the feed circuit in the called station a throttling coil, a control relay series-connected to said throt tling coil adapted to close said circuit, a condenser, a high sensitive larized relay seriesconnected to said condenser said condenser and said polarized relay in arallel connection with said series-connec 1i throttling coil and control relay, an auxiliary circuit, contacis on said control relay adapted to close said auxiliary circuit, a typing electromagnet, a conveying electromet in said auxiliary circuit controlling said typing electromagnet, and a contact of said high stance polarized relay operating said typing electromagnet.

10. An arrangement'as specified in cla 1, comprising in the called station a switch device consisting of oscillatable contact arm, a releasing contact being closed by said Ken arm at the beginning of its operative oscillation, an auxiliary contact opened at the beginning of the operative oscillation of said arm, a second auxiliary contact, and a con-.

trol contact both adapted to be closed at the end of the operative oscillation of said arm so that the feed circuit is closed and the I caller circuitcut'out, said control contact and second mentioned auxiliary contact adapted to be opened at the beginning of the retrograde oscillation of said contact arm said releasing contact maintaining said feed circuit closed until the transmitter si s have been recorded .said throttling coll seriesconnected with said control relay alter the closing of the feedcircuit so that in the loop in the called station a decrease of current intensity occurs the voltage in the arrangement being thereby increased In testimony whereof we a our signa- 12o tures.

EGON ZOLLER. JOSEF VILLIGERI.

erative oscillation of said arm so that the feed circuit is closed and the caller circuit cut out, said control contact and second mentioned auxiliary contact adapted to be opened at v 

